By Tommy H. Thomason

Monday, January 19, 2009

It Seemed Like a Good Idea at the Time

As jet airplanes flew faster, hydraulic assist on the pitch and roll control surfaces became necessary. Since this added weight and complexity, Grumman tried to avoid a powered control system in the design of the XF10F.  The horizontal tail was positioned by much smaller version of the tail which the pilot controlled directly without any hydraulic assist. Roll control was accomplished by lift-spoiling tabs that rose vertically out of the wing, with some additional control and the requisite "feel" provided by small ailerons. Unfortunately, neither pitch nor roll control approach was successful, with the lag in pitch control making the aircraft all but unflyable.

In this picture of the spin test model, the small tail surface is pointed down, which forced the leading edge of the big tail surface down, leading to the stall that would precede a spin with the rudder, ailerons, and right wing spoiler tabs positioned as shown here. (The leading edge wing slats are shown out since they extended aerodynamically as the airplane approached a stall.)

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